Ordered Structure of a Distorted C602- Fulleride Ion

We now report the experimental observation of a distortion in the crystal structure of the PPN[sup +] salt of C[sub 60][sup 2[minus]] (PPN[sup +] = bis(triphenylphosphine)iminium ion). This is the first single-crystal structure of a C[sub 60][sup [minus]] salt, and it is highly ordered. The packing diagram shows that the C[sub 60][sup 2[minus]] anion sits at a center of symmetry and is completely surrounded by PPN[sup +] cations. There are at least 22 phenyl groups (11 symmetry-related pairs) that closely approach the C[sub 60][sup 2[minus]] unit. They are derived from five distinct pairs of cations on a 4,3,2,1,1 basis. The C[sub 60][sup 2[minus]] ion shows a small but significant distortion from icosahedral symmetry. In summary, we have provided the first structural proof of distortion in C[sub 60][sup n[minus]] ions. All C[sub 60][sup n[minus]] ions up to n = 5 have Jahn-Teller degenerate electronic states and may show related distortions. 12 refs., 3 figs., 1 tab.